The importance of a solar cell has been recognized as a clean energy source, and a demand for such a solar cell is increasing. The solar cell is used in various technical fields ranging from power sources for large electric equipment to small power sources for precision electronic devices. If the solar cell is to be widely used in various technical fields, then characteristics of the solar cell, particularly, an output characteristic of the solar cell should be precisely measured. Otherwise, various inconveniences in use of the solar cell may possibly occur. Therefore, especially a technique is demanded which is available to tests, measurements and experiments of the solar cell and which can irradiate a large area with highly-precise simulated sunlight. Major requirements which the simulated sunlight should meet are (i) to make an emission spectrum of the simulated sunlight similar to that of the standard sunlight (set by the Japanese Industrial Standards) and (ii) to make an irradiance of the simulated sunlight substantially equal to that of the standard sunlight. In view of such requirements, a simulated sunlight irradiation apparatus has been developed as a device for irradiating simulated sunlight that meets such requirements. Generally, the simulated sunlight irradiation apparatus is used for measuring an amount of power generated by the solar cell by irradiating a light receiving surface of the solar cell with artificial light (simulated sunlight) whose irradiance is uniform.
For example, Patent Literature 1 discloses a method for calculating by simulation an amount of power generated by solar photovoltaic power generation. This method is for obtaining an amount of power generated by a solar cell in consideration of influences of regional difference, characteristic values of an individual solar cell, an installation mount, and the like. More specifically, Patent Literature 1 discloses a method for obtaining an amount of power generated by a solar cell by first preparing a voltage-current curve (I-V curve) and a power-voltage curve (P-V curve) for specified solar irradiance and solar cell temperature according to a basic characteristic formula for solar cells. This makes it possible to obtain a more precise amount of power generated by a solar cell in consideration of influences of regional difference, characteristic values of an individual solar cell, an installation mount, and the like.